Service oriented architecture (SOA) is a business-driven IT architectural approach that supports integrating business processes as linked, repeatable business tasks, or services as defined in service documents. A service document is a basic building block of SOA that defines how a service can be used, accessed and managed with other services. Service documents are used by analysts, architects, and developers during a development phase of the SOA life cycle to locate services to reuse and to evaluate the impact of changes to service configurations. Service documents are variously described as metadata, objects, descriptions, entities and artifacts that store information about a service including a service description and a service endpoint. A service endpoint is a unique computer addressable location for the service. Service documents are stored in a service registry within an SOA system. Information in each service document, including the service endpoints, is indexed in a process known as shredding. Indexing service documents to maintain a list of all services and service endpoints is a part of maintaining on demand services. An example of a service registry is IBM® WebSphere® Service Registry & Repository. The registry may highlight that there are several endpoints available to route the service request. When a request comes in, the registry can use its knowledge of the available service architecture topology and note that the service requested is either not available or is performing below the agreed service level agreement.
Installed services having a registered service endpoint can be invoked, whereas, services without a registered endpoint cannot be invoked. Services are installed in a service provider with a fixed or readily available service endpoint defined in the service document and indexed by a service registry. However, many service providers have fixed resources and have to prioritize high demand services over low demand services; therefore, not all services are available at the same time.
A low demand service may be uninstalled from a service provider and removed from the service provider's active services; any service endpoint associated with the service will be removed by the registry and the service archived so that it requires re-installation and setting up with a new service endpoint. It would be useful for a customer to request an uninstalled service and not experience any delay or difference in service. A low demand or uninstalled service many sometimes be referred to as legacy or an underused service.
The service provider may, instead of uninstalling, lower the processing priority of a low demand service or in some other way reduce processing bandwidth given to the low demand service. This could have the effect of reducing the quality of service experienced by the service requester to the point where the service was not what the service requester wanted. In some cases, the reduction in quality would be contrary to the terms of the service contract. It would be useful for a service requester to receive a desired quality of service and not experience a delay or difference in quality of service even if the requested service had had its processing priority lowered and needed to be reconfigured.